U.S. patent application number 16/061434 was filed with the patent office on 2019-05-02 for plasma processing apparatus.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. The applicant listed for this patent is TOKYO ELECTRON LIMITED. Invention is credited to Yuki HOSAKA, Toshiki NAKAJIMA, Mayo UDA, Yoshihiro UMEZAWA.
Application Number | 20190131136 16/061434 |
Document ID | / |
Family ID | 59056376 |
Filed Date | 2019-05-02 |
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United States Patent
Application |
20190131136 |
Kind Code |
A1 |
HOSAKA; Yuki ; et
al. |
May 2, 2019 |
PLASMA PROCESSING APPARATUS
Abstract
A plasma processing apparatus includes a baffle plate, a
shutter, and a driving device. The baffle plate has a cylindrical
shape, and has a plurality of through holes formed in a sidewall
thereof. The shutter has a cylindrical shape and is provided around
the baffle plate to be movable in an axial direction of the baffle
plate along the sidewall of the baffle plate. The driving device
moves the shutter along the sidewall of the baffle plate. The
plurality of through holes are disposed in the sidewall of the
baffle plate so that synthesized conductance of the through holes,
which are not covered by the shutter, is increased with respect to
a movement amount of the shutter as the shutter is moved
downward.
Inventors: |
HOSAKA; Yuki; (Miyagi,
JP) ; UMEZAWA; Yoshihiro; (Miyagi, JP) ;
NAKAJIMA; Toshiki; (Miyagi, JP) ; UDA; Mayo;
(Miyagi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOKYO ELECTRON LIMITED |
Tokyo |
|
JP |
|
|
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
59056376 |
Appl. No.: |
16/061434 |
Filed: |
December 2, 2016 |
PCT Filed: |
December 2, 2016 |
PCT NO: |
PCT/JP2016/085873 |
371 Date: |
June 12, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J 37/32633 20130101;
H05H 1/46 20130101; H01L 21/3065 20130101; H01J 37/32816
20130101 |
International
Class: |
H01L 21/3065 20060101
H01L021/3065; H01J 37/32 20060101 H01J037/32; H05H 1/46 20060101
H05H001/46 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 16, 2015 |
JP |
2015-245450 |
Claims
1. A plasma processing apparatus that performs plasma processing on
a workpiece, the plasma processing apparatus comprising: a
processing container; a placement table provided in the processing
container and configure to place the workpiece thereon; a
cylindrical baffle plate having a plurality of through holes formed
in a sidewall thereof, and defining a processing space above the
placement table and a gas discharge space around the placement
table; a cylindrical shutter having an inner circumferential
surface having a diameter larger than a diameter of an outer
circumferential surface of the baffle plate, is the shutter being
provided around the baffle plate to be movable in an axial
direction of the baffle plate along the sidewall of the baffle
plate; and a driving device configured to change synthesized
conductance made by the plurality of through holes, which are not
covered by the shutter, by moving the shutter along the sidewall of
the baffle plate, wherein the plurality of through holes are
disposed in the sidewall of the baffle plate such that a change
amount of the synthesized conductance of the through holes, which
are not covered by the shutter, is increased with respect to a
movement amount of the shutter as the shutter is moved
downward.
2. The plasma processing apparatus of claim 1, wherein assuming
that, for each of regions of the sidewall of the baffle plate
through which an upper end of the shutter passes when the position
of the shutter is changed by a predetermined distance, a number,
which is assigned in the ascending order to the regions in an order
that the upper end of the shutter passes when the shutter is moved
downward, is defined as s, conductance of each of the through holes
is defined as C.sub.h, an inclination of a straight line indicating
a change in pressure in the processing container with respect to a
targeted movement amount of the shutter is defined as -.alpha., a
segment of the straight line is defined as .beta., and a mass flow
rate of gas supplied into the processing space is defined as Q, the
number n(s) of the through holes disposed in the region indicated
by the number s satisfies Equation 1 as follows. .alpha. C q ( C q
.beta. - C q .alpha. s ) 2 = n ( s ) C q = C h Q [ Equation 1 ]
##EQU00007##
3. The plasma processing apparatus of claim 2, wherein the through
holes, which are disposed in the regions, respectively, are
disposed in the regions such that intervals between adjacent
through holes in the regions are uniform.
4. The plasma processing apparatus of claim 2, wherein an opening
area of each of the through holes disposed in the region to which
the number s having a large value is assigned is larger than an
opening area of each of the through holes disposed in the region to
which the number s having a small value is assigned.
5. The plasma processing apparatus of claim 1, wherein each of the
through holes is disposed in the sidewall of the baffle plate such
that each of the through holes less overlap other through holes in
the axial direction of the baffle plate.
Description
TECHNICAL FIELD
[0001] Various aspects and exemplary embodiments of the present
disclosure relate to a plasma processing apparatus.
BACKGROUND
[0002] In the manufacturing of semiconductor devices or electronic
devices such as flat panel displays (FPDs), a plasma processing is
performed on workpieces in order to process the workpieces. For
example, a plasma processing apparatus used for the plasma
processing has a processing container, a placement table, a gas
supply unit, and a gas discharge device. The placement table is
provided in the processing container, and the gas supply unit and
the gas discharge device are connected to a space within the
processing container.
[0003] Recently, two or more plasma processing processes, which are
performed under different pressure conditions, are required to be
continuously performed in a single plasma processing apparatus. In
the plasma processing processes in which pressure varies, it is
advantageous to shorten a period of time for which pressure varies,
that is, a transition time. In order to shorten the pressure
transition time, it is advantageous to decrease the volume of a
space in which a workpiece is disposed.
[0004] As a plasma processing apparatus that meets these
requirements, there has been proposed, for example, a plasma
processing apparatus disclosed in Patent Document 1. The plasma
processing apparatus disclosed in Patent Document 1 has two baffle
plates interposed between a placement table and a processing
container. A first space disposed above the two baffle plates
includes a region in which a workpiece is disposed, and a gas
supply unit is connected to the first space. In addition, a gas
discharge device is connected to a second space disposed below the
two baffle members.
[0005] The two baffle plates are circular plates that extend
horizontally, a plurality of openings are formed in the two baffle
plates, and the openings are arranged circumferentially. In the
plasma processing apparatus disclosed in Patent Document 1, a
degree to which the openings of the two baffle plates vertically
overlap one another is adjusted by rotating one of the two baffle
plates circumferentially. Therefore, in the plasma processing
apparatus disclosed in Patent Document 1, conductance between the
first space and the second space is adjusted such that the pressure
in the first space is adjusted.
PRIOR ART DOCUMENT
Patent Document
[0006] Patent Document 1: Japanese Patent Application Laid-Open No.
2001-196313
DISCLOSURE OF THE INVENTION
Problems to be Solved
[0007] By the way, in the plasma processing apparatus disclosed in
Patent Document 1, it is difficult to set the pressure in the first
space to high pressure unless an interval between the two baffle
plates is set to be extremely small. That is, it is difficult to
decrease the conductance between the first space and the second
space unless the interval between the two baffle plates is set to
be extremely small. However, when the interval between the two
baffle plates is decreased, the baffle plates come into contact
with each other and particles are produced in some instances.
[0008] It is necessary to increase thicknesses of the two baffle
plates in order to allow the contact between the two baffle plates
or precisely configure the two baffle plates such that a gap
between the two baffle plates becomes small. However, in a case in
which the thicknesses of the two baffle plates are large, the
conductance between the first space and the second space is not
greatly increased even though the two baffle plates are disposed so
that the openings of the two baffle plates overlap one another. For
this reason, it is difficult to decrease the pressure in the first
space. Therefore, in the plasma processing apparatus disclosed in
Patent Document 1, it is difficult to improve controllability of
pressure in the processing space in which a workpiece is disposed.
Further, a method of increasing sizes of the openings of the two
baffle plates is considered to decrease the pressure in the first
space, but plasma penetrates into the second space in the case in
which the sizes of the openings are increased.
[0009] Weights of the baffle plates are increased when the
thicknesses of the two baffle plates are increased. Therefore, a
size of a driving device for driving the baffle plates is
increased. Therefore, it is not practical to increase the thickness
of the baffle plate or increase the size of the opening formed in
the baffle plate.
Means to Solve the Problems
[0010] One aspect of the present disclosure provides a plasma
processing apparatus that performs plasma processing on a
workpiece. The plasma processing apparatus includes a processing
container, a placement table, a baffle plate, a shutter, and a
driving device. The placement table is provided in the processing
container, and the workpiece is placed on the placement table. The
baffle plate has a cylindrical shape, and a plurality of through
holes are formed in a sidewall thereof. The baffle plate defines a
processing space above the placement table and a gas discharge
space around the placement table. The shutter has a cylindrical
shape, and has an inner circumferential surface having a diameter
larger than a diameter of an outer circumferential surface of the
baffle plate. The shutter is provided around the baffle plate to be
movable in an axial direction of the baffle plate along the
sidewall of the baffle plate. The driving device changes
synthesized conductance made by the multiple through holes, which
are not covered by the shutter, by moving the shutter along the
sidewall of the baffle plate. In addition, the plurality of through
holes are disposed in the side surface of the baffle plate such
that a change amount in synthesized conductance of the through
holes, which are not covered by the shutter, is increased with
respect to a movement amount of the shutter as the shutter is moved
downward.
Effect of the Invention
[0011] According to various aspects and exemplary embodiments of
the present disclosure, there is provided a plasma processing
apparatus capable of improving controllability of pressure in a
processing space in which a workpiece is disposed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a view schematically illustrating an example of a
plasma processing apparatus.
[0013] FIG. 2 is a perspective view schematically illustrating
examples of a first cylindrical portion of a baffle plate and a
second cylindrical portion of a shutter.
[0014] FIG. 3 is a perspective view schematically illustrating the
examples of the first cylindrical portion of the baffle plate and
the second cylindrical portion of the shutter.
[0015] FIG. 4 is a partially broken perspective view illustrating
the examples of the baffle plate and the shutter.
[0016] FIG. 5 is a schematic view illustrating an example of an
arrangement of through holes formed in a first cylindrical portion
of a baffle plate according to Example 1.
[0017] FIG. 6 is a block diagram illustrating an example of a
control system related to control of the shutter.
[0018] FIG. 7 is a view illustrating a first cylindrical portion of
a baffle plate according to a Comparative Example.
[0019] FIG. 8 is a view illustrating an experimental result of
pressure control according to the Comparative Example.
[0020] FIG. 9 is a view illustrating an example of a targeted
change in pressure.
[0021] FIG. 10 is a view illustrating an example of a targeted
change in conductance.
[0022] FIG. 11 is a view illustrating an example of synthesized
conductance of the through holes in a region corresponding to each
stroke.
[0023] FIG. 12 is a view illustrating an example of an arrangement
of through holes according to Example 1.
[0024] FIG. 13 is a view illustrating an example of a simulation
result of pressure control according to Example 1.
[0025] FIG. 14 is a view illustrating another example of the
arrangement of the through holes formed in the first cylindrical
portion of the baffle plate.
[0026] FIG. 15 is a view illustrating an example of an arrangement
of through holes formed in a first cylindrical portion of a baffle
plate according to Example 2.
[0027] FIG. 16 is a view illustrating an example of an evaluation
result of pressure control according to Example 2.
[0028] FIG. 17 is a view illustrating examples of the number and
the radii of through holes disposed in a region corresponding to
each stroke.
[0029] FIG. 18 is a view illustrating another example of pressure
control.
[0030] FIG. 19 is a view illustrating another example of the
arrangement of the through holes formed in the first cylindrical
portion of the baffle plate.
[0031] FIG. 20 is a view illustrating another example of pressure
control.
[0032] FIG. 21 is a view illustrating an example of pressure pulse
control.
DETAILED DESCRIPTION TO EXECUTE THE INVENTION
[0033] Hereinafter, exemplary embodiments of a disclosed plasma
processing apparatus will be described in detail with reference to
the drawings. Further, the disclosed disclosure is not limited to
the present exemplary embodiments.
EXAMPLE 1
Configuration of Plasma Processing Apparatus 10
[0034] FIG. 1 is a view schematically illustrating an example of a
plasma processing apparatus 10. FIG. 1 schematically illustrates a
longitudinal sectional structure of the plasma processing apparatus
10. The plasma processing apparatus 10 illustrated in FIG. 1 is a
capacitively-coupled parallel flat plate plasma etching apparatus.
The plasma processing apparatus 10 has a processing container 12.
The processing container 12 is configured by, for example, aluminum
having an anodized surface. The processing container 12 has a
sidewall 12s. The sidewall 12s has an approximately cylindrical
shape. An axis Z indicates a central axis of the sidewall 12s. An
opening 12g for loading or unloading a wafer W, which is an example
of a workpiece, is formed in the sidewall 12s. The opening 12g is
configured to be openable or closable by a gate valve 52.
[0035] A placement table 14 is provided in the processing container
12. The placement table 14 is supported by a support unit 16. The
support unit 16 is an insulating member having an approximately
cylindrical shape and extends upward from a bottom portion of the
processing container 12. In the present Example, the support unit
16 is in contact with a lower circumferential edge portion of the
placement table 14 and supports the placement table 14.
[0036] The placement table 14 includes a lower electrode 18 and an
electrostatic chuck 20. The lower electrode 18 has an approximately
disk shape and is made of a conductor. A first high-frequency power
source HFS is connected to the lower electrode 18 via a matching
device MU1. The first high-frequency power source HFS is a power
source that mainly generates high-frequency electric power for
producing plasma, and for example, the first high-frequency power
source HFS generates high-frequency electric power of 27 MHz to 100
MHz. In the present Example, the first high-frequency power source
HFS generates, for example, high-frequency electric power of 40
MHz. The matching device MU1 matches output impedance of the first
high-frequency power source HFS with input impedance at a load side
(lower electrode 18 side).
[0037] A second high-frequency power source LFS is connected to the
lower electrode 18 via a matching device MU2. The second
high-frequency power source LFS mainly generates high-frequency
electric power (high-frequency bias electric power) for implanting
ions into the wafer W, and supplies the high-frequency bias
electric power to the lower electrode 18. A frequency of the
high-frequency bias electric power is, for example, a frequency
within a range of 400 kHz to 13.56 MHz. In the present Example, the
second high-frequency power source LFS supplies high-frequency bias
electric power of, for example, 3 MHz to the lower electrode 18.
The matching device MU2 matches output impedance of the second
high-frequency power source LFS with input impedance at the load
side (lower electrode 18 side).
[0038] The electrostatic chuck 20 is provided on the lower
electrode 18. The electrostatic chuck 20 has a structure in which
an electrode 20a, which is a conductive film, is disposed between a
pair of insulating layers or insulating sheets. A direct current
power source 22 is electrically connected to the electrode 20a via
a switch SW. An upper surface of the electrostatic chuck 20 defines
a placement region 20r in which the wafer W is placed. When direct
current voltage is applied from the direct current power source 22
to the electrode 20a of the electrostatic chuck 20, the
electrostatic chuck 20 draws and holds the wafer W placed in the
placement region 20r with electrostatic force such as Coulomb's
force.
[0039] The plasma processing apparatus 10 is provided with a focus
ring FR that surrounds an edge of the wafer W. The focus ring FR is
made of, for example, silicon or quartz.
[0040] A flow path 18a is formed in the lower electrode 18. A
refrigerant such as a coolant is supplied to the flow path 18a
through a pipe 26a from a chiller unit provided outside the plasma
processing apparatus 10. The refrigerant supplied to the flow path
18a returns back to the chiller unit through a pipe 26b. A
temperature of the refrigerant, which circulates in the flow path
18a, is controlled by the chiller unit such that a temperature of
the wafer W placed on the electrostatic chuck 20 is controlled.
[0041] A pipe 28 is provided in the placement table 14. The pipe 28
supplies heat transfer gas, such as He gas, which is supplied from
a heat transfer gas supply mechanism, to a portion between the
upper surface of the electrostatic chuck 20 and a rear surface of
the wafer W.
[0042] The plasma processing apparatus 10 has an upper electrode
30. The upper electrode 30 is disposed above the lower electrode 18
so as to face the lower electrode 18. The lower electrode 18 and
the upper electrode 30 are provided in the processing container 12
so as to be approximately in parallel with each other.
[0043] The upper electrode 30 is supported on a ceiling portion of
the processing container 12 through an insulating shielding member
32. The upper electrode 30 includes an electrode plate 34 and an
electrode support body 36. The electrode plate 34 faces a space in
the processing container 12 and has a plurality of gas discharge
holes 34a. The electrode plate 34 is made of a conductor or a
semiconductor with low Joule heat and low resistance.
[0044] The electrode support body 36 is made of a conductive
material such as aluminum and supports the electrode plate 34 so
that the electrode plate 34 is detachable. The electrode support
body 36 has a water-cooled structure. A gas diffusion chamber 36a
is provided in the electrode support body 36. A plurality of gas
flow holes 36b, which communicate with the gas discharge holes 34a,
extend downward from the gas diffusion chamber 36a. In addition, a
gas introducing port 36c, which introduces processing gas into the
gas diffusion chamber 36a, is formed in the electrode support body
36. A gas supply pipe 38 is connected to the gas introducing port
36c.
[0045] A gas source group 40 is connected to the gas supply pipe 38
via a valve group 42 and a flow rate controller group 44. The gas
source group 40 has a plurality of gas sources. The plurality of
gas sources are sources having a plurality of different types of
gases. The valve group 42 has a plurality of valves. The flow rate
controller group 44 has a plurality of flow rate controllers. Each
of the flow rate controllers is, for example, a mass flow
controller or the like. Each of the gas sources of the gas source
group 40 is connected to the gas supply pipe 38 via one valve of
the valve group 42 and one flow rate controller of the flow rate
controller group 44.
[0046] In the plasma processing apparatus 10, gas from one or more
gas sources selected from the plurality of gas sources of the gas
source group 40 is supplied to the gas supply pipe 38 in a state in
which a flow rate of the gas is controlled by the corresponding
flow rate controller and the corresponding valve. The gas supplied
into the gas supply pipe 38 is diffused into the gas diffusion
chamber 36a and supplied into the space in the processing container
12 through the gas flow holes 36b and the gas discharge hole 34a.
Further, in the present Example, the gas source group 40, the flow
rate controller group 44, the valve group 42, the gas supply pipe
38, and the upper electrode 30 constitute a gas supply unit GS. The
gas supply unit GS is connected to a first space S1 to be described
below.
[0047] As illustrated in FIG. 1, a gas discharge pipe 48 is
connected to the bottom portion of the processing container 12, and
a gas discharge device 50 is connected to the gas discharge pipe
48. The gas discharge device 50 is connected to a second space S2
to be described below via the gas discharge pipe 48. The gas
discharge device 50 has a vacuum pump such as a turbo molecular
pump.
[0048] The plasma processing apparatus 10 has a control unit Cnt.
For example, the control unit Cnt is a computer having a processor,
a storage unit, an input device, a display device, and the like,
and controls respective parts of the plasma processing apparatus
10. The control unit Cnt receives, through the input device, an
operator's operation of inputting a command for managing the plasma
processing apparatus 10. In addition, the control unit Cnt
visualizes and displays, on the display device, an operational
situation of the plasma processing apparatus 10, and the like. In
addition, the storage unit of the control unit Cnt stores a control
program for controlling various types of processes to be performed
in the plasma processing apparatus 10 by the processor or a
program, that is, a processing recipe or the like for performing
processing on respective configurations of the plasma processing
apparatus 10 in accordance with processing conditions.
[0049] In the plasma processing apparatus 10 configured as
described above, gas is supplied into the processing container 12
from one or more gas sources selected from the plurality of gas
sources of the gas source group 40 in order to process the wafer W.
Further, as high-frequency electric power for producing plasma is
applied to the lower electrode 18, a high-frequency electric field
is generated between the lower electrode 18 and the upper electrode
30. With the high-frequency electric field, plasma of the gas
supplied into the processing container 12 is produced. Further, the
wafer W, which is drawn and held on the electrostatic chuck 20, is
processed, for example, etched by the produced plasma. Further,
ions may be implanted into the wafer W by applying the
high-frequency bias electric power to the lower electrode 18.
[0050] [Baffle Structure 60]
[0051] For example, as illustrated in FIG. 1, the plasma processing
apparatus 10 further includes a baffle structure 60. The baffle
structure 60 is disposed between the placement table 14 and the
sidewall 12s of the processing container 12 below the placement
region 20r. The baffle structure 60 defines the first space S1 and
the second space S2 in the processing container 12. The first space
S1 is a space including a space above the placement table 14. The
second space S2 is a space around the placement table 14. The
aforementioned gas supply unit GS is connected to the first space
S1, and the aforementioned gas discharge device 50 is connected to
the second space S2. The first space S1 is an example of a
processing space, and the second space S2 is an example of a gas
discharge space.
[0052] Next, the description will be made with reference to FIGS. 2
to 4 together with FIG. 1. FIGS. 2 and 3 are perspective views
schematically illustrating examples of a first cylindrical portion
61a of a baffle plate 61 and a second cylindrical portion 62a of a
shutter 62. FIG. 4 is a breakaway perspective view illustrating the
examples of the baffle plate 61 and the shutter 62. Further, FIGS.
2 to 4 are views illustrated for the sake of understanding of the
description. For this reason, an aspect ratio between the first
cylindrical portion 61a and the second cylindrical portion 62a and
the size and the number of through holes 61h formed in the first
cylindrical portion 61a, which are illustrated in FIGS. 2 to 4, are
different from the actual aspect ratio between the first
cylindrical portion 61a and the second cylindrical portion 62a and
the actual size and the actual number of through holes 61h formed
in the first cylindrical portion 61a. For example, as illustrated
in FIGS. 1 and 4, the baffle structure 60 includes the baffle plate
61 and the shutter 62.
[0053] [Structure of Baffle Plate 61]
[0054] For example, the baffle plate 61 is made by coating a
surface of metal such as aluminum or stainless steel with a coating
such as Y.sub.2O.sub.3. The baffle plate 61 has the first
cylindrical portion 61a, a lower annular portion 61b, and an upper
annular portion 61c. The first cylindrical portion 61a is an
example of a sidewall of the baffle plate 61.
[0055] For example, as illustrated in FIG. 1 and FIGS. 2 to 4, the
first cylindrical portion 61a has an approximately cylindrical
shape and is provided in the processing container 12 so that a
central axis of the first cylindrical portion 61a approximately
coincides with the axis Z. In the present Example, a plate
thickness of the first cylindrical portion 61a is, for example, 5
mm. In addition, in the present Example, a diameter of an outer
circumferential surface of the first cylindrical portion 61a is,
for example, 550 mm. For example, as illustrated in FIG. 1, the
first cylindrical portion 61a is provided between the placement
table 14 and the sidewall 12s of the processing container 12.
[0056] For example, as illustrated in FIG. 1 and FIGS. 2 to 4, the
plurality of through holes 61h are formed in the first cylindrical
portion 61a. Each of the through holes 61h penetrates the first
cylindrical portion 61a radially (i.e., in a radial direction) with
respect to the axis Z. In the present Example, an opening of each
of the through holes 61h has an approximately circular shape, and a
radius of the through hole 61h is, for example, 1 mm. In the
present Example, shapes and areas of the openings of the through
holes 61h are equal to one another. Further, as another example,
the opening of each of the through holes 61h may have an elliptical
shape, a long circular shape, a polygonal shape, or the like.
[0057] For example, as illustrated in FIGS. 1 and 4, the lower
annular portion 61b has an annular shape. The lower annular portion
61b is continuously connected to a lower end of the first
cylindrical portion 61a and extends radially inward from the lower
end of the first cylindrical portion 61a. In addition, the upper
annular portion 61c has an annular shape. The upper annular portion
61c is continuously connected to an upper end of the first
cylindrical portion 61a and extends radially outward from the upper
end of the first cylindrical portion 61a. In the present Example,
the first cylindrical portion 61a, the lower annular portion 61b,
and the upper annular portion 61c of the baffle plate 61 are
integrally formed, for example. Further, as another example, the
first cylindrical portion 61a, the lower annular portion 61b, and
the upper annular portion 61c may be made as separate members, and
the baffle plate 61 may be made by assembling the first cylindrical
portion 61a, the lower annular portion 61b, and the upper annular
portion 61c.
[0058] For example, as illustrated in FIG. 1, the bottom portion of
the processing container 12 includes an approximately cylindrical
support portion 12m. A cylindrical member 64 is provided above the
support portion 12m. The cylindrical member 64 is made of, for
example, an insulator such as ceramic. The cylindrical member 64
extends along an outer circumferential surface of the support unit
16. In addition, an annular member 66 is provided on the
cylindrical member 64 and the support unit 16. The annular member
66 is made of, for example, an insulator such as ceramic. The
annular member 66 extends to the vicinity of an edge of the
electrostatic chuck 20 along an upper surface of the lower
electrode 18. The aforementioned focus ring FR is provided on the
annular member 66.
[0059] An inner edge portion of the lower annular portion 61b of
the baffle plate 61 is disposed between the support portion 12m and
the cylindrical member 64. The support portion 12m and the
cylindrical member 64 are coupled to each other by, for example, a
screw. Therefore, the inner edge portion of the lower annular
portion 61b of the baffle plate 61 is interposed and supported
between the support portion 12m and the cylindrical member 64.
[0060] For example, as illustrated in FIG. 1, the sidewall 12s of
the processing container 12 includes an upper portion 12s1 and a
lower portion 12s2. In addition, the plasma processing apparatus 10
has a support member 68. The support member 68 has an upper portion
68a having an approximately annular shape, and a lower portion 68c
having an approximately annular shape. The upper portion 68a and
the lower portion 68c are connected to each other via an
intermediate portion having an approximately cylindrical shape. The
upper portion 68a of the support member 68 is interposed and
supported between the upper portion 12s1 and the lower portion 12s2
of the sidewall 12s. In addition, the lower portion 68c of the
support member 68 extends radially inward in the processing
container 12. The upper annular portion 61c of the baffle plate 61
is fixed to the lower portion 68c of the support member 68 by, for
example, a screw. In the present Example, the upper portion 68a,
the intermediate portion, and the lower portion 68c of the support
member 68 are integrally formed, for example. Further, as another
example, the upper portion 68a, the intermediate portion, and the
lower portion 68c may be made as separate members, and the support
member 68 may be made by assembling the upper portion 68a, the
intermediate portion, and the lower portion 68c.
[0061] [Structure of Shutter 62]
[0062] For example, the shutter 62 may be made by coating a surface
of metal such as aluminum or stainless steel with a coating such as
Y.sub.2O.sub.3. For example, as illustrated in FIGS. 1 and 4, the
shutter 62 has the second cylindrical portion 62a and an annular
portion 62b. For example, as illustrated in FIG. 1 and FIGS. 2 to
4, the second cylindrical portion 62a has an approximately
cylindrical shape and is provided in the processing container 12 so
that a central axis of the second cylindrical portion 62a
approximately coincides with the axis Z. In addition, a diameter of
an inner circumferential surface of the second cylindrical portion
62a is larger than a diameter of an outer circumferential surface
of the first cylindrical portion 61a of the baffle plate 61. In the
present Example, the diameter of the inner circumferential surface
of the second cylindrical portion 62a is, for example, 550.1 mm,
and a plate thickness of the second cylindrical portion 62a is, for
example, 5 mm. Further, in the present Example, the diameter of the
outer circumferential surface of the first cylindrical portion 61a
is, for example, 550 mm, and a central axis of the first
cylindrical portion 61a and a central axis of the second
cylindrical portion 62a approximately coincide with the axis Z.
Therefore, for example, as illustrated in FIG. 3, a gap GP of, for
example, 0.1 mm is present between an outer circumference of the
first cylindrical portion 61a and an inner circumference of the
second cylindrical portion 62a. Therefore, the second cylindrical
portion 62a may be moved in a direction of the axis Z along the
first cylindrical portion 61a without coming into contact with the
first cylindrical portion 61a. For this reason, it is possible to
inhibit particles from being produced when the shutter 62 is moved
along the first cylindrical portion 61a of the baffle plate 61.
[0063] For example, as illustrated in FIGS. 1 and 4, the annular
portion 62b of the shutter 62 has an approximately annular shape.
In the present Example, the annular portion 62b is continuously
connected to a lower end of the second cylindrical portion 62a and
extends radially outward. In the present Example, the second
cylindrical portion 62a and the annular portion 62b of the shutter
62 are integrally formed, for example. Further, as another example,
the second cylindrical portion 62a and the annular portion 62b may
be made as separate members, and the shutter 62 may be made by
assembling the second cylindrical portion 62a and the annular
portion 62b.
[0064] For example, as illustrated in FIG. 1, the annular portion
62b of the shutter 62 is connected to a shaft body 69. In the
present Example, the shaft body 69 is, for example, a feed screw,
and the annular portion 62b is connected to the shaft body 69 by a
nut. In addition, the shaft body 69 is connected to a driving
device 70. The driving device 70 is, for example, a motor. The
driving device 70 moves the shutter 62 upward and downward along
the shaft body 69. Therefore, the second cylindrical portion 62a of
the shutter 62 is moved upward and downward between the first
cylindrical portion 61a of the baffle plate 61 and the sidewall 12s
of the processing container 12. Further, while FIG. 1 illustrates
the single shaft body 69, but the plurality of shaft bodies 69,
which are arranged circumferentially, may be connected to the
annular portion 62b of the shutter 62.
[0065] For example, as illustrated in FIGS. 2 and 3, the second
cylindrical portion 62a of the shutter 62 may be moved upward and
downward by the driving device 70 in the direction of the axis Z
along the outer circumferential surface of the first cylindrical
portion 61a. When the second cylindrical portion 62a is moved
downward, the number of through holes 61h, which are covered by the
second cylindrical portion 62a, is decreased. Therefore,
synthesized conductance of the baffle structure 60, which is made
by the plurality of through holes 61h that are not covered by the
second cylindrical portion 62a, is increased.
[0066] For example, as illustrated in FIG. 2, when the shutter 62
is positioned at a lowermost side within a movement range of the
shutter 62, none of the through holes 61h formed in the first
cylindrical portion 61a are covered by the second cylindrical
portion 62a. That is, all of the through holes 61h formed in the
first cylindrical portion 61a communicate directly with the second
space S2. Therefore, the synthesized conductance of the baffle
structure 60, which is made by the plurality of through holes 61h
that are not covered by the second cylindrical portion 62a, is
maximized. Therefore, the pressure in the first space S1 becomes
close to the pressure in the second space S2 such that the pressure
in the first space S1 may be set to low pressure.
[0067] When the second cylindrical portion 62a is moved upward, the
number of through holes 61h, which are covered by the second
cylindrical portion 62a, is increased. Therefore, the synthesized
conductance of the baffle structure 60, which is made by the
plurality of through holes 61h that are not covered by the second
cylindrical portion 62a, is decreased. Further, for example, as
illustrated in FIG. 3, when the shutter 62 is positioned at an
uppermost side within the movement range of the shutter 62, the
through holes 61h, except for the through holes 61h formed at an
uppermost stage of the first cylindrical portion 61a, are covered
by the second cylindrical portion 62a. Therefore, the synthesized
conductance of the baffle structure 60, which is made by the
plurality of through holes 61h that are not covered by the second
cylindrical portion 62a, is minimized. Therefore, the pressure in
the first space S1 becomes higher than the pressure in the second
space S2 such that the pressure in the first space S1 may be set to
high pressure.
[0068] Here, the baffle plate 61 and the shutter 62 have an
approximately cylindrical shape such that in comparison with a case
in which the baffle plate 61 and the shutter 62 have a disk shape,
the structure of the baffle plate 61 and the structure of the
shutter 62 are hardly deformed by an influence of the pressure in
the first space S1. For this reason, it is possible to ensure
mechanical strength even without greatly increasing thicknesses of
the baffle plate 61 and the shutter 62. Therefore, the synthesized
conductance of the baffle structure 60 may be sufficiently low when
the shutter 62 is moved to the uppermost position, and the
synthesized conductance of the baffle structure 60 may be
sufficiently high when the shutter 62 is moved to the lowermost
position. Therefore, the plasma processing apparatus 10 of the
present Example may improve controllability of pressure in the
first space S1.
[0069] For example, as illustrated in FIG. 3, the gap GP is present
between the first cylindrical portion 61a and the second
cylindrical portion 62a. For this reason, in the case in which the
shutter 62 is positioned at the uppermost side within the movement
range of the shutter 62, the synthesized conductance of the baffle
structure 60 is the synthesized conductance of conductance of the
respective through holes 61h formed at the uppermost stage of the
first cylindrical portion 61a and conductance of a flow path formed
by the gap GP and the through holes 61h except for the
aforementioned through holes 61h. Therefore, in the case in which
the shutter 62 is positioned at the uppermost side within the
movement range of the shutter 62, the synthesized conductance of
the baffle structure 60 has a higher value than the synthesized
conductance of the respective through holes 61h formed at the
uppermost stage of the first cylindrical portion 61a.
[0070] [Arrangement of Through Holes 61h]
[0071] Here, an arrangement of the plurality of through holes 61h
formed in the first cylindrical portion 61a will be described with
reference to FIG. 5. FIG. 5 is a schematic view illustrating an
example of an arrangement of the through holes 61h formed in the
first cylindrical portion 61a of the baffle plate 61 according to
Example 1. For example, as illustrated in FIG. 5, in the first
cylindrical portion 61a, one or more through holes 61h are disposed
in each region 61r for each predetermined length in the direction
of the axis Z. For example, as illustrated in FIG. 5, in the first
cylindrical portion 61a, each of the regions 61r extends in a
direction intersecting the direction of the axis Z, for example,
each of the regions 61r extends in a direction orthogonal to the
direction of the axis Z. In the present Example, for example, as
illustrated in FIG. 5, a width of each of the regions 61r in the
direction of the axis Z is approximately equal to a diameter of the
through hole 61h disposed in the region 61r. Therefore, it is
possible to decrease the movement range of the shutter 62 when
controlling the pressure in the first space S1 by moving the
shutter 62.
[0072] The plurality of regions 61r are disposed in the direction
of the axis Z, and one or more through holes 61h are disposed in
each of the regions 61r. For this reason, the number of through
holes 61h, which are not covered by the second cylindrical portion
62a of the shutter 62, is increased as the shutter 62 is moved
downward. For this reason, the synthesized conductance of the
through holes 61h, which are not covered by the second cylindrical
portion 62a, is increased as the shutter 62 is moved downward. In
the present Example, values of conductance of the respective
through holes 61h are approximately equal to one another since the
shapes and the areas of the openings of the respective through
holes 61h are approximately equal to one another. For this reason,
if the numbers of through holes 61h included in the respective
regions 61r are equal to one another, the change amount in
synthesized conductance of the through holes 61h, which are not
covered by the second cylindrical portion 62a, is constant with
respect to the movement amount of the shutter 62.
[0073] In contrast, in the present Example, the through holes 61h
are disposed in the first cylindrical portion 61a of the baffle
plate 61 so that the change amount in synthesized conductance of
the through holes 61h, which are not covered by the second
cylindrical portion 62a, is increased with respect to the movement
amount of the shutter 62 as the shutter 62 is moved downward. For
example, in a range of the position of the shutter 62 at which the
number of through holes 61h, which are covered by the second
cylindrical portion 62a, is larger than a first number, the change
amount in synthesized conductance of the through holes 61h, which
are not covered by the second cylindrical portion 62a, with respect
to the movement amount of the shutter 62 is defined as
.DELTA.C.sub.1. In addition, in a range of the position of the
shutter 62 at which the number of through holes 61h, which are
covered by the second cylindrical portion 62a, is smaller than the
first number, the change amount in synthesized conductance of the
through holes 61h, which are not covered by the second cylindrical
portion 62a, with respect to the movement amount of the shutter 62
is defined as .DELTA.C.sub.2. In the case in which .DELTA.C.sub.1
and .DELTA.C.sub.2 are defined as described above, the through
holes 61h are disposed in the first cylindrical portion 61a of the
baffle plate 61 so that .DELTA.C.sub.1<.DELTA.C.sub.2 is
satisfied.
[0074] In the present Example, since the values of conductance of
the respective through holes 61h are approximately equal to one
another, the through holes 61h are disposed in the first
cylindrical portion 61a of the baffle plate 61 so that for example,
as illustrated in FIG. 5, in the region 61r below the second region
61r from the top side, the number of through holes 61h included in
the region 61r is increased as the position of the region 61r is
lowered.
[0075] In the present Example, the number of through holes 61h
included in the region 61r at the uppermost stage is set to the
number by which conductance for achieving predetermined pressure as
an initial value is implemented. Therefore, in the present Example,
the number of through holes 61h included in the region 61r at the
uppermost stage becomes larger than the number of through holes 61h
included in the second region 61r from the top side.
[0076] In each of the regions 61r on the first cylindrical portion
61a, the through holes 61h disposed in the region 61r are disposed
in the region 61r so that intervals between the adjacent through
holes 61h in the region 61r are approximately uniform. In addition,
the respective through holes 61h are disposed in the first
cylindrical portion 61a so that the respective through holes 61h
less overlap the other through holes 61h in the direction of the
axis Z. Therefore, it is possible to inhibit a flow of gas passing
through the plurality of through holes 61h from circumferentially
deviating.
[0077] The respective regions 61r are regions on the first
cylindrical portion 61a through which the upper end of the second
cylindrical portion 62a passes when a stroke caused by the movement
of the shutter 62 is changed by one step. In the present Example,
the stroke is a position of the shutter 62 in the direction of the
axis Z.
[0078] The shutter 62 is moved by a predetermined distance in the
direction of the axis Z, and numbers s, which are integers, are
assigned to the respective strokes of the shutter 62 in the
ascending order from 1 from the top side to the bottom side. For
example, when the shutter 62 is positioned at the uppermost side as
illustrated in FIG. 3, the number of the stroke of the shutter 62
at this position is 1. Further, when the shutter 62 is moved
downward by a predetermined distance, the number of the stroke of
the shutter 62 at the position after the shutter 62 is moved is 2.
Hereinafter, the stroke, to which a number having a value of s is
assigned, is referred to as a stroke s.
[0079] Numbers, which are integers, are assigned to the respective
regions 61r in the ascending order from 1 from the top side to the
bottom side. The numbers, which are assigned to the respective
regions 61r, correspond to the numbers of the strokes of the
shutter 62. For example, when the shutter 62 is moved from a stroke
s-1 to the stroke s, the upper end of the second cylindrical
portion 62a passes through the region 61r to which the number s is
assigned.
[0080] For example, when the value of the stroke of the shutter 62
is 1, the upper end of the second cylindrical portion 62a is
positioned between the region 61r positioned at the uppermost side
and the region 61r adjacent to and below the region 61r positioned
at the uppermost side. Since the number assigned to the region 61r
positioned at the uppermost side is 1, only the region 61r to which
the number 1 is assigned is not covered by the second cylindrical
portion 62a of the shutter 62 when the value of the stroke of the
shutter 62 is 1. In addition, when the value of the stroke of the
shutter 62 is n, the upper end of the second cylindrical portion
62a is positioned between the region 61r to which the number n is
assigned and the region 61r to which the number n+1 is assigned and
which is adjacent to and below the region 61r to which the number n
is assigned. For this reason, when the value of the stroke of the
shutter 62 is n, a portion from the region 61r to which the number
1 is assigned to the region 61r to which the number n is assigned
is not covered by the second cylindrical portion 62a of the shutter
62. In addition, when the value of the stroke of the shutter 62 is
a maximum value s.sub.max, the upper end of the second cylindrical
portion 62a is positioned at a lower end of the region 61r to which
the number s.sub.max is assigned. For this reason, when the value
of the stroke of the shutter 62 is s.sub.max, none of the regions
61r are covered by the second cylindrical portion 62a of the
shutter 62. Further, hereinafter, the region 61r to which the
number s, which is equal to the number s of the stroke, is
assigned, is referred to as the region 61r corresponding to the
stroke s.
[0081] In the present Example, the number of through holes 61h
covered by the shutter 62 is large at a position of the shutter 62
at which the value of the stroke is small, and the number of
through holes 61h covered by the shutter 62 is small at a position
of the shutter 62 at which the value of the stroke is large.
[0082] FIG. 6 is a block diagram illustrating an example of a
control system related to control of the shutter 62. For example,
as illustrated in FIG. 6, the driving device 70 is controlled by
the control unit Cnt. The control unit Cnt receives signals from a
displacement meter 90, a pressure gauge 92, and a pressure gauge
94. The displacement detector 90 measures a distance from a
position of the shutter 62 or from a reference position in the
direction of the axis Z, and transmits a signal, which indicates a
measurement result, to the control unit Cnt. The pressure gauge 92
measures the pressure in the first space S1, and transmits a
signal, which indicates a measurement result, to the control unit
Cnt. The pressure gauge 94 measures the pressure in the second
space S2, and transmits a signal, which indicates a measurement
result, to the control unit Cnt.
[0083] Based on the signals indicating the measurement results from
the pressure gauge 92 and the pressure gauge 94, the control unit
Cnt calculates a position of the shutter 62 in the direction of the
axis Z at which the pressure in the first space S1 becomes pressure
designated by the recipe. Further, based on the calculated position
of the shutter 62 and the signal indicating the measurement result
from the displacement meter 90, the control unit Cnt calculates the
movement amount of the shutter 62. Further, the control unit Cnt
transmits a signal, which indicates the calculated movement amount
of the shutter 62, to the driving device 70. Based on the signal
from the control unit Cnt, the driving device 70 moves the shutter
62 in the direction of the axis Z.
[0084] According to the plasma processing apparatus 10 configured
as described above, it is possible to adjust a proportion of the
plurality of through holes 61h covered by the second cylindrical
portion 62a to the second space S2 by adjusting a positional
relationship in the vertical direction between the first
cylindrical portion 61a of the baffle plate 61 and the second
cylindrical portion 62a of the shutter 62. Therefore, it is
possible to adjust conductance between the first space S1 and the
second space S2. Therefore, it is possible to set the pressure in
the first space S1 to any pressure.
COMPARATIVE EXAMPLE
[0085] Here, controllability of pressure in the processing
container 12 in a case in which a baffle plate 61 according to a
Comparative Example is used will be described. FIG. 7 is a view
illustrating a first cylindrical portion 61a' of the baffle plate
61 according to the Comparative Example. For example, as
illustrated in FIG. 7, a plurality of through holes 61h' are formed
in the first cylindrical portion 61a' of the baffle plate 61
according to the Comparative Example. Each of the through holes
61h' has a longitudinal slit shape in the vertical direction. The
through holes 61h' are arranged circumferentially with respect to
the axis Z at an approximately uniform pitch so that the through
holes 61h' are distributed around the entire first cylindrical
portion 61a'.
[0086] [Change in Pressure in First Space S1 according to
Comparative Example]
[0087] FIG. 8 is a view illustrating an experimental result of
pressure control according to the Comparative Example. In FIG. 8,
the vertical axis indicates the pressure in the first space S1, and
the horizontal axis indicates the stroke of the shutter 62. As the
shutter 62 is moved downward, a proportion of the respective
through holes 61h' formed in the first cylindrical portion 61a',
which are covered by the second cylindrical portion 62a of the
shutter 62, is decreased. For this reason, synthesized conductance
of the baffle structure 60 according to the Comparative Example is
increased by moving the shutter 62 downward. Therefore, the
pressure in the first space S1 is decreased by moving the shutter
62 downward.
[0088] However, as apparent from FIG. 8, the pressure in the first
space S1 is rapidly decreased in accordance with the movement of
the shutter 62 in a region in which a proportion of the respective
through holes 61h' covered by the shutter 62 is high (a region in
which the value of the stroke is small). Meanwhile, in a region in
which a proportion of the respective through holes 61h' covered by
the shutter 62 is low (a region in which the value of the stroke is
large), the amount of decrease in pressure in the first space S1 is
small even though the shutter 62 is moved. For this reason, it is
difficult to set the pressure in the first space S1 to a desired
pressure by controlling the stroke of the shutter 62. That is, in
the plasma processing apparatus 10 according to the Comparative
Example, controllability of pressure is low when controlling the
pressure in the first space S1 by the shutter 62.
[0089] [Method of Determining Arrangement of Through Holes 61h]
[0090] Here, an arrangement of the through holes 61h formed in the
first cylindrical portion 61a of the baffle plate 61 according to
the present Example will be described. To improve controllability
of pressure when controlling the pressure in the first space S1 by
moving the shutter 62, the pressure in the first space S1 may be
linearly changed with respect to the movement amount of the shutter
62. For example, FIG. 9 illustrates an ideal change in pressure in
the first space S1 with respect to the stroke of the shutter 62.
FIG. 9 is a view illustrating an example of a targeted change in
pressure. In the example in FIG. 9, the pressure in the first space
S1 is linearly changed with respect to the strokes of 1 to 50.
[0091] For example, in a case in which the pressure in the first
space S1 is rectilinearly changed with respect to the stroke, the
pressure P(s) in the first space S1 in the case in which the
shutter 62 is positioned at the stroke s is expressed as follows
using the stroke s as a variable.
[ Equation 1 ] P ( s ) = P min - P max S max - 1 s + P min - P min
- P max S max - 1 S max ( 1 ) ##EQU00001##
[0092] Here, P.sub.max indicates the pressure in the first space S1
at the position of the shutter 62 at which the value of the stroke
s is 1. In the present Example, the through holes 61h at the
uppermost stage of the first cylindrical portion 61a are not
covered by the second cylindrical portion 62a even though the
shutter 62 is positioned at the uppermost side. In addition,
P.sub.min indicates the pressure in the first space S1 at the
position of the shutter 62 at which the value of the stroke s is a
maximum value S.sub.max.
[0093] P(s) indicated in Equation 1 is considered as a linear
function related to the variable s, and as indicated below, an
inclination is set to .alpha., and a segment is set to .beta..
[ Equation 2 ] P min - P max S max - 1 = .alpha. P min - P min - P
max S max - 1 S max = .beta. } ( 2 ) ##EQU00002##
[0094] Therefore, a straight line indicated in the aforementioned
Equation 1 is expressed as the following Equation 3.
[Equation 3]
P(s)=.alpha.s+.beta. (3)
[0095] When an inclination of the straight line illustrated in FIG.
9 is set to -.alpha., the following relationship is satisfied so
that the straight line expressed as the aforementioned Equation 3
becomes the straight line illustrated in FIG. 9.
[ Equation 4 ] d ds P ( s ) = - .alpha. ( 4 ) ##EQU00003##
[0096] Here, it has been known that assuming that a mass flow rate
of gas supplied into the processing container 12 is Q, synthesized
conductance C of the baffle structure 60 when the pressure in the
first space S1 is P(s) is generally obtained from the following
Equation.
[ Equation 5 ] C = Q P ( s ) ( 5 ) ##EQU00004##
[0097] The result of plotting the synthesized conductance C
indicated in the aforementioned Equation 5 for each stroke of the
shutter 62 is as illustrated in FIG. 10, for example. FIG. 10 is a
view illustrating an example of a targeted change in conductance.
As apparent from FIG. 10, the change amount in synthesized
conductance C with respect to the stroke s is small in the range in
which the value of the stroke s is small, and the change amount in
synthesized conductance C with respect to the stroke s is large in
the range in which the value of the stroke s is large. When the
synthesized conductance of the baffle structure 60 is changed as
illustrated in FIG. 10 as the stroke s of the shutter 62 is
controlled, the pressure in the first space S1 may be changed as
illustrated in FIG. 9.
[0098] In the present Example, when the shutter 62 is positioned at
the position of the stroke s, the through holes 61h, which are
disposed between the region 61r corresponding to the stroke having
a value of 1 and the region 61r corresponding to the stroke having
a value of s, are not covered by the shutter 62. Assuming that the
synthesized conductance of the through holes 61h disposed in one
region 61r corresponding to the stroke s of the shutter 62 is C(s),
the aforementioned Equation 5 may be expressed as follows, for
example.
[ Equation 6 ] .intg. 2 s C ( s ) ds = C = Q P ( s ) ( 6 )
##EQU00005##
[0099] In the present Example, when the value of the stroke s of
the shutter 62 is 1, the shutter 62 is positioned at the uppermost
side, and only the through holes 61h at the uppermost stage of the
first cylindrical portion 61a are not covered by the second
cylindrical portion 62a of the shutter 62. Further, when the value
of the stroke s is 1, the synthesized conductance of the baffle
structure 60 is set as conductance for achieving predetermined
pressure as an initial value. Further, the number of through holes
61h or the sizes of openings of the through holes 61h at the
uppermost stage of the first cylindrical portion 61a are determined
in order to realize the conductance set as the initial value.
[0100] The result of plotting, based on the aforementioned Equation
6, the synthesized conductance C(s) of the through holes 61h
disposed in the respective regions 61r of the first cylindrical
portion 61a for each stroke s is as illustrated in FIG. 11, for
example. FIG. 11 is a view illustrating an example of the
synthesized conductance C(s) of the through holes 61h in the region
61r corresponding to each stroke s. As apparent from FIG. 11, the
change amount in synthesized conductance C(s) of the through holes
61h in the region 61r corresponding to the stroke s is small in the
range in which the value of the stroke s is small, and the change
amount in synthesized conductance C(s) of the through holes 61h in
the region 61r corresponding to the stroke s is large in the range
in which the value of the stroke s is large.
[0101] Assuming that the conductance of the respective through
holes 61h is C.sub.h and the number of through holes 61h in the
region 61r corresponding to the stroke s is n(s) for each stroke s
having a value of 2 or more, the synthesized conductance C(s) of
the through holes 61h in the region 61r corresponding to the stroke
s is expressed as follows.
[Equation 7]
C(s)=C.sub.h.times.n(s) (7)
[0102] Here, in the present Example, each of the through holes 61h
has an approximately cylindrical shape. For this reason, the
conductance C.sub.h of each of the through holes 61h is synthesized
conductance of conductance C.sub.o of an orifice and conductance
C.sub.L of a circular conduit.
[0103] Here, assuming that a ratio between the conductance C.sub.h
of each of the through holes 61h and the mass flow rate Q of the
gas is C.sub.Q (=C.sub.h/Q), the number n(s) of through holes 61h
in the region 61r corresponding to the stroke s for each stroke s
may be determined as follows.
[ Equation 8 ] n ( s ) = .alpha. C q ( C q .beta. - C q .alpha. s )
2 ( 8 ) ##EQU00006##
[0104] In a case in which the value of n(s) calculated based on the
aforementioned Equation 8 is not an integer, the value of n(s) is
changed to an integer value by rounding off, up, or down the value
to the nearest integer to remove a value below a decimal point.
[0105] As the through holes 61h of which the number calculated
based on Equation 8 is n(s) are disposed in the first cylindrical
portion 61a of the baffle plate 61, the synthesized conductance of
the baffle structure 60 is changed with respect to the change in
stroke of the shutter 62, as illustrated in FIG. 10, for example.
That is, the through holes 61h are disposed in the first
cylindrical portion 61a of the baffle plate 61 so that the number
of through holes 61h in the region 61r corresponding to each stroke
s is equal to the number n(s) calculated based on Equation 8 such
that the plurality of through holes 61h are disposed in the first
cylindrical portion 61a of the baffle plate 61 so that the change
amount in synthesized conductance of the through holes 61h, which
are not covered by the second cylindrical portion 62a, is increased
with respect to the movement amount of the shutter 62 as the
shutter 62 is moved downward.
[0106] [Simulation Result]
[0107] FIG. 12 is a view illustrating an example of an arrangement
of the through holes 61h according to Example 1. FIG. 12
illustrates a result of calculating the number n(s) of through
holes 61h in the region 61r corresponding to each stroke s using
the aforementioned Equation 8 and the following values of
parameters. Further, for example, N.sub.2 gas is considered as gas
supplied into the processing container 12.
[0108] Mass flow rate Q=0.845 Pam.sup.3/s
[0109] Radius of opening of through hole 61h a=1 mm
[0110] Average velocity v=470.4 m/s
[0111] Thickness of first cylindrical portion 61a L=5 mm
[0112] Maximum value of stroke S.sub.max=25
[0113] Maximum value of pressure P.sub.max=66.67 Pa (500 mT)
[0114] Minimum value of pressure P.sub.min=4 Pa (30 mT)
[0115] Simulation was performed on the change in pressure in the
first space S1 using the baffle plate 61 in which the through holes
61h of which the number is the number n(s) illustrated in FIG. 12
are disposed in the region 61r corresponding to each stroke s. FIG.
13 is a view illustrating an example of a simulation result of
pressure control according to Example 1. In FIG. 13, the vertical
axis indicates the pressure in the first space S1, and the
horizontal axis indicates the stroke s of the shutter 62. As
apparent from FIG. 13, the pressure in the first space S1 is
linearly changed with respect to the change amount in stroke s of
the shutter 62. Therefore, the plasma processing apparatus 10 of
the present Example may precisely set the pressure in the first
space S1 to any pressure by controlling the stroke s of the shutter
62 within a control range from the maximum value P.sub.max of the
pressure to the minimum value P.sub.min of the pressure. Therefore,
the plasma processing apparatus 10 of the present Example may
improve controllability of pressure when controlling the pressure
in the first space S1 by moving the shutter 62.
[0116] In the present Example, the areas of the openings of the
respective through holes 61h formed in the first cylindrical
portion 61a of the baffle plate 61 are approximately equal to one
another. For this reason, the plurality of through holes 61h are
disposed in the region 61r of the baffle plate 61 corresponding to
a position of the shutter 62 at which the value of the stroke s is
large. As the number of through holes 61h formed in the baffle
plate 61 is increased, manufacturing costs of the baffle plate 61
are increased, or a length of a sum of diameters of the through
holes 61h formed in the respective regions 61r exceeds a
circumferential length of the first cylindrical portion 61a in some
instances. For this reason, in the region 61r in which the number
of through holes 61h is large, several through holes 61h, which are
integrated into a single through holes 61h2, may be formed in the
first cylindrical portion 61a, as illustrated in FIG. 14, for
example. However, in this case, a value of conductance of the
through hole 61h2 may be approximately equal to a value of
synthesized conductance of the respective through holes 61h
integrated into the through hole 61h2. FIG. 14 is a view
illustrating another example of an arrangement of the through holes
61h formed in the first cylindrical portion 61a of the baffle plate
61.
[0117] Example 1 has been described above. As apparent from the
aforementioned description, the plasma processing apparatus 10 of
the present example may improve controllability of the pressure in
the first space S1.
EXAMPLE 2
[0118] Next, Example 2 will be described. In the plasma processing
apparatus 10 according to Example 2, the through holes 61h are
formed in the first cylindrical portion 61a of the baffle plate 61
so that the areas of the openings of the through holes 61h in the
region 61r corresponding to the stroke s are increased as the value
of the stroke s is increased. Further, because the configuration of
the plasma processing apparatus 10 except for the first cylindrical
portion 61a is identical to that of the plasma processing apparatus
10 according to Example 1, which has been described with respect to
FIGS. 1 to 4, except for the following description, a detailed
description thereof will be omitted.
[0119] [Arrangement of Through Holes 61h]
[0120] FIG. 15 is a view illustrating an example of an arrangement
of the through holes 61h formed in the first cylindrical portion
61a of the baffle plate 61 according to Example 2. For example, as
illustrated in FIG. 15, in the first cylindrical portion 61a of the
baffle plate 61 according to the present Example, the areas of the
openings of the through holes 61h disposed in the respective
regions 61r are increased as the value of the stroke s of the
shutter 62 is increased, that is, toward the lower side of the
first cylindrical portion 61a. In the present Example, since the
shape of each of the openings of the through holes 61h has an
approximately circular shape, a radius a of the through hole 61h
disposed in each of the regions 61r is increased toward the lower
side of the first cylindrical portion 61a in the present Example.
For example, in the first cylindrical portion 61a illustrated in
FIG. 15, a diameter .phi.2 of the through hole 61h disposed in the
region 61r corresponding to the stroke s having a value of 10 is
larger than a diameter .phi.1 of through hole 61h disposed in the
region 61r corresponding to the stroke s having a value of 1.
[0121] Even in the present Example, the plurality of through holes
61h are disposed in the first cylindrical portion 61a of the baffle
plate 61 so that the change amount in synthesized conductance of
the through holes 61h, which are not covered by the second
cylindrical portion 62a, is increased with respect to the movement
amount of the shutter 62 as the shutter 62 is moved downward.
[0122] Here, in the case in which the areas of the openings of the
respective through holes 61h are equal to one another, the number
of through holes 61h in the region 61r corresponding to the
position of the shutter 62 at which the value of the stroke is
large is larger than the number of through holes 61h in the region
61r corresponding to the position of the shutter 62 at which the
value of the stroke is small. Manufacturing costs of the baffle
plate 61 are increased as the number of through holes 61h formed in
the first cylindrical portion 61a of the baffle plate 61 is
increased. Therefore, in the present Example, the number of through
holes 61h formed in the first cylindrical portion 61a is reduced by
increasing the areas of the openings of the through holes 61h in
the region 61r corresponding to the stroke having a large value.
Therefore, it is possible to improve controllability of pressure
and inhibit an increase in costs of the plasma processing apparatus
10.
[0123] [Evaluation Result]
[0124] FIG. 16 is a view illustrating an example of an evaluation
result of pressure control according to Example 2. In the
evaluation result illustrated in FIG. 16, for example, the baffle
plate 61, which has the through holes 61h disposed in the region
61r corresponding to each stroke so that the radius a and the
number n(s) illustrated in FIG. 17 are made, is used. As indicated
by the actual measurement values in FIG. 16, in the plasma
processing apparatus 10 of the present Example, the pressure in the
first space S1 is changed rectilinearly in accordance with an
increase in stroke of the shutter 62. Therefore, even in the plasma
processing apparatus 10 of the present Example, it is possible to
realize high controllability related to the pressure control.
Further, in the data illustrated in FIG. 16, there are differences
between the actual measurement values and the simulation values,
but the reason is that a value of the gap GP set in the simulation
is different from a value of the gap GP in an actual apparatus.
[0125] Example 2 has been described above. As apparent from the
aforementioned description, the plasma processing apparatus 10 of
the present Example may improve controllability of the pressure in
the first space S1. Further, according to the plasma processing
apparatus 10 of the present Example, it is possible to inhibit an
increase in costs of the plasma processing apparatus 10.
[0126] [Others]
[0127] The disclosed technology is not limited to the
aforementioned Examples and may be variously modified within the
subject matter thereof.
[0128] For example, in the respective Examples, the change in
pressure in the first space S1 with respect to the change in stroke
of the shutter 62 is controlled to be changed along the single
straight line, but the disclosed technology is not limited thereto.
For example, as illustrated in FIG. 18, the range of the stroke
from 1 to the maximum value is divided into a plurality of small
ranges .DELTA.s.sub.1 to .DELTA.s.sub.3, and the through holes 61h
may be disposed in the respective regions 61r of the baffle plate
61 so that the pressure in the first space S1 is changed along
straight lines having different inclinations for each small range.
In this case, the number n(s) of through holes 61h included in the
region 61r corresponding to each stroke s in the small region is
determined for each small region using a targeted inclination of a
change in pressure in the first space S1 and using the
aforementioned Equation 8. Further, in the example in FIG. 18, the
range of the stroke from 1 to the maximum value is divided into the
three small ranges .DELTA.s.sub.1 to .DELTA.s.sub.3, but the number
of divided small ranges is not limited to three, and the number of
divided small ranges may be two, or four or more.
[0129] For example, as illustrated in FIG. 19, in the first
cylindrical portion 61a of the baffle plate 61, the through holes
61h may be disposed, for example, only in the region 61r
corresponding to the stroke having a value of 1 and the region 61r
corresponding to the stroke having a value of s.sub.1. In this
case, the conductance of the baffle structure 60 is rapidly
increased when the shutter 62 is moved downward and the stroke
reaches s.sub.1. Therefore, for example, as illustrated in FIG. 20,
the pressure in the first space S1 may be rapidly changed based on
the position of the shutter 62 at which the value of the stroke is
s.sub.1.
[0130] For example, as illustrated in FIG. 21, the pressure in the
first space S1 may be alternately changed in a pulse shape by, for
example, reciprocally moving the stroke of the shutter 62 at a
constant speed within a range of 1 to s.sub.max using the first
cylindrical portion 61a illustrated in FIG. 19. Assuming that in
the change in pressure in a pulse shape illustrated in FIG. 21, a
ratio of a period of time .DELTA.T.sub.1 of high pressure to a
period of time .DELTA.T.sub.0 of 1 cycle is defined as a duty
ratio, the duty ratio corresponds to a ratio of a distance L.sub.1
to a distance L.sub.0 illustrated in FIG. 19. The distance L.sub.0
illustrated in FIG. 19 is a distance from a lower end of the region
61r corresponding to the stroke s having a value of 1 to a lower
end of the region 61r corresponding to the stroke s having a value
of s.sub.max. In addition, the distance L.sub.1 illustrated in FIG.
19 is a distance from a lower end of the region 61r corresponding
to the stroke s having a value of 1 to a lower end of the region
61r corresponding to the stroke s having a value of s.sub.1.
[0131] The pulse control of pressure with any duty ratio may also
be implemented by controlling the driving device 70 so as to change
the stroke s of the shutter 62 from s.sub.i-1 to s.sub.1 at a
predetermined timing and change the stroke s of the shutter 62 from
s.sub.1 to s.sub.1-1 at a predetermined timing.
[0132] A width of each of the regions 61r in the direction of the
axis Z is approximately equal to a diameter of the through hole 61h
disposed in the region 61r. For this reason, in Example 2, in a
case in which the number of regions 61r including the through holes
61h having a large radius is excessively increased, a movement
range of the shutter 62 is increased, and it is difficult to reduce
a size of the plasma processing apparatus 10. Therefore, in a case
in which a length of a sum of widths of all of the regions 61r in
the direction of the axis Z exceeds a predetermined length, the
through holes 61h may be substituted with the through holes 61h
having a small radius in the order from the region 61r in which the
number n(s) of through holes 61h is small until the length of the
sum of the widths of all of the regions 61r in the direction of the
axis Z becomes smaller than the predetermined length. Therefore, it
is possible to inhibit an increase in costs of the plasma
processing apparatus 10 within a range in which the size of the
plasma processing apparatus 10 may be reduced.
DESCRIPTION OF SYMBOLS
[0133] W: Wafer
[0134] 10: Plasma processing apparatus
[0135] 12: Processing container
[0136] 14: Placement table
[0137] 20: Electrostatic chuck
[0138] 30: Upper electrode
[0139] 34: Electrode plate
[0140] 36: Electrode support body
[0141] 48: Gas discharge pipe
[0142] 50: Gas discharge device
[0143] 60: Baffle structure
[0144] 61: Baffle plate
[0145] 61h: Through hole
[0146] 62: Shutter
[0147] 70: Driving device
* * * * *